Red giants are dying stars, in an advanced stage of stellar evolution, with their cores depleted of hydrogen.
But in a study recently published in Nature Communications, astronomers have found new evidence that the cores of red giants undergo dramatic structural changes.
The interiors of stars cannot yet be directly observed, but astroseismic techniques can measure vibrations induced by gravitational and acoustic waves inside stars, reflecting the physical properties of their interiors.
Using data from the Kepler Space Telescope, the researchers analyzed the vibrational frequencies of 359 low-mass red giants by astroseismic methods and found discontinuities in the internal structure of nearly 7 percent of the sample of stars.
The researchers suggest that these discontinuities may have been “smoothed out” by some unknown physical process, but have influenced the subsequent evolution of the stars.
The study also found that the inner layers of low-mass red giants have helium.
The physical phenomenon of helium burning in the inner layers of low-mass red giants is often used as an astronomical “probe” to determine galaxy densities and probe the chemical evolution of galaxies.
Therefore, it is important to understand the causes of these discontinuities in order to accurately model and exploit red giants.